1. Field
The following description relates to a wireless communication system, and more particularly, to a power amplifier to amplify and output an output signal of a wireless communication system.
2. Description of the Related Art
A wireless communication system amplifies a radio-frequency (RF) signal using a power amplifier (PA) prior to transmission over an antenna and outputs the amplified RF signal.
A power amplifier amplifies an incoming RF signal according to a bias voltage and outputs the amplified RF signal through an antenna. In amplifying an RF signal, to prevent heat loss due to a difference between a voltage of a signal output from the antenna and a fixed bias voltage, an envelope tracking (ET) power amplifier is used. The ET power amplifier shifts a bias voltage level according to the change in the amplitude of an input RF signal.
As described above, although the ET power amplifier is more advanced in efficiency than a fixed-bias-type power amplifier, there may be a problem that distortion may occur due to data loss when a power amplifier bias signal and an input RF signal of the power amplifier are not synchronized with each other.